Difference Between SD vs SDHC vs SDXC Memory Cards

SD stands for Secure Digital. They have a small lock on them which prevents the data from being erased mistakenly. SD, SDHC and SDXC are various types of SD (Secure Digital) format, that have been released in that order by the SD Association.

SD stands for Secure Digital.SDHC stands for Secure Digital High Capacity.
And SDXCstands for Secure Digital eXtended Capacity.
Other formats include miniSD and microSD but modern DSLRs don’t support them..

All major SD card manufacturers like Panasonic, SanDisk Corporation and Toshiba Corporation established the SD Association in January 2000. The SD Association is a global ecosystem of companies setting industry-leading memory card standards that simplify the use and extend the life of consumer electronics, including mobile phones, for millions of people every day.

The Association does not manufacture, market or sell any product; it exists to create standards and then promote the adoption, advancement and use of SD standards used by competing product manufacturers that make interoperable memory cards and devices.

As requirements for higher capacities came in, SD cards have grown in capacity too (SDHC is SD High Capacity, while SDXC is SD Xtended Capacity). SDHC cards typically come in capacities between 4GB to 32GB. SDXC cards come in sizes of 32GB of higher, with a theoretical maximum of 2TB.

Backwards compatibility is built in, so if a camera has SDHC support , it will support standard SD cards too. If a camera or device has SDXC support, it will support SD and SDHC. These cards have speed ratings too; Class 2, 4, 6, 10 and so on, with Class 10 having the fastest read-write performance.

Various Speed/Class of SD Cards

The other type is MMC or MultiMedia Cards which may look similar to SD cards, but they are an older format. If you look carefully, you’ll notice that MMC cards do not have the tiny lock slider switch that SD cards have; the lock prevents data being written to or deleted from the card. Most cameras that support SD cards will also support the use of MMC cards.

When it comes to memory cards, you will never have enough of them. So, it’s better to have a few cards as back up. Generally its better to have few cards of lower capacity, rather than one or two cards with a huge capacity, in case of failure, theft, loss etc. Memory cards are pretty reliable, but they do fail sometimes especially if you don’t format them properly.